• Composites Research
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• v.23 no.2
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• pp.17-23
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• 2010

The stealth technology can increase the survivability of aircrafts or warships and enhance the capability of mission completion in hostile territory. The purpose of this paper is to present the low observable structure with curved surfaces made by fiber-reinforced composites and to show the possibility of developing omnidirectional stealth platforms for military applications. In this study, we developed a radar absorbing structures(RAS) based on a circuit analog absorber to reduce the radar cross section(RCS) of an object with curved surfaces. Firstly, the RAS with a periodic square patterned conducting polymer layer was designed and simulated using a commercial 3-D electromagnetic field analysis program. Secondly, the designed semi-cylindrical structure with low RCS was fabricated using fiber-reinforced composites and conducting polymer. To make the periodic pattern layer, acts as resistive sheet, the intrinsic conducting polymer paste containing PEDOT with a polyurethane binder was used. Finally, the radar cross section was measured to evaluate the radar absorbing performances of the fabricated RAS by the compact range facility in POSTECH.

• Journal of Aerospace System Engineering
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• v.8 no.4
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• pp.24-31
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• 2014

The modern version of aircrafts is allowed to guarantee the superior handing qualities within the entire flight envelope by imposing the adequate stability and flying qualities on a target aircraft through the various techniques of flight control law design. Generally, the flight control law of the aircraft in service applies the various techniques of the verified control algorithm, such as dynamic inversion and eigenstructure assignment. The supersonic trainer employs the RSS(Relaxed Static Stability) concept in order to improve the aerodynamic performance in longitudinal axis and the longitudinal control laws employ the dynamic inversion with proportional-plus-integral control method. And, lateral-directional control laws employ the blended roll system of both beta-betadot feedback and simple roll rate feedback with proportional control method in order to guarantee aircraft stability. In this paper, the lateral-directional flight control law is designed by applying dynamic inversion control technique as a different method from the current supersonic trainer control technique, where the roll rate command system is designed at the lateral axis for the rapid response characteristics, and the sideslip command system is adopted at the directional axis for stability augmentation. The dynamic inversion of a simple 1st order model is applied. And this designed flight control law is confirmed to satisfy the requirement presented from the military specification. This study is expected to contribute to design the flight control law of KF-X(Korean Fighter eXperimental) which will proceed into the full-scale development in the near future.

• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.70-80
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• 2022

An aerial refueling provides for extension of operational time and range for aircraft and enhances mission effectiveness, hence it application by most military aircrafts. The receiver aircraft should have the aerial refueling clearance that is established by performing technical and operational compatibility assessments to certify it for aerial refueling with a specific tanker model. The compatibility assessment includes aerial refueling handling qualities, functional, fuel, lighting system testing and it is finally verified through flight testing. However, since aerial refueling compatibility assessments have never been performed in Korea, there is no experience to determine the test requirements and the scope and size of the test program for a new development aircraft. This paper therefore introduces the common techniques of aerial refueling and aerial refueling flight test methods to understand the aerial refueling FCS (Flight Control System), OFP (operational flight program) and system validation, and aerial refueling envelope clearance of a fixed wing aircraft for a boom and receptacle refueling system that is being introduced into Korea Air Force.

• The Korean Journal of Air & Space Law and Policy
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• v.28 no.1
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• pp.3-54
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• 2013

Nowadays, major advanced countries in aviation technology are putting their effort to develop commercial and civil Unmanned Aircraft System(UAS) due to its highly promising market demand in the future. The market scale of commercial and civil UAS is expected to increase up to approximately 8.8 billon U.S. dollars by the year 2020. The usage of commercial and civil UAS covers various areas such as remote sensing, relaying communications, pollution monitoring, fire detection, aerial reconnaissance and photography, coastline monitoring, traffic monitoring and control, disaster control, search and rescue, etc. With the introduction of UAS, changes need to be made on current Air Traffic Management Systems which are focused mainly manned aircrafts to support the operation of UAS. Accordingly, the legislation for the UAS operation should be followed. Currently, ICAO's Unmanned Aircraft System Study Group(UASSG) is leading the standardization process of legislation for UAS operation internationally. However, some advanced countries such as United States, United Kingdom, Australia have adopted its own legislation. Among these countries, United States is most forth going with President Obama signing a bill to integrate UAS into U.S. national airspace by 2015. In case of Korea, legislation for the unmanned aircraft system is just in the beginning stage. There are no regulations regarding the operation of unmanned aircraft in Korea's domestic aviation law except some clauses regarding definition and permission of the unmanned aircraft flight. However, the unmanned aircrafts are currently being used in military and under development for commercial use. In addition, the Ministry of Land, Infrastructure and Transport has a ambitious plan to develop commercial and civil UAS as Korea's most competitive area in aircraft production and export. Thus, Korea is in need of the legislation for the UAS operation domestically. In this regards, I personally think that Korea's domestic legislation for UAS operation will be enacted focusing on following 12 areas : (1)use of airspace, (2)licenses of personnel, (3)certification of airworthiness, (4)definition, (5)classification, (6)equipments and documents, (7)communication, (8)rules of air, (9)training, (10)security, (11)insurance, (12)others. Im parallel with enacting domestic legislation, korea should contribute to the development of international standards for UAS operation by actively participating ICAO's UASSG.